1. Technical Field
The present invention relates to broadband signal distribution equipment for distributing communication signals, and, in particular, to a method and apparatus of broadband signal distribution whereby interference with the broadband signal distribution can be prevented when access to an enclosure housing the distribution equipment is authorized.
2. Description of the Prior Art
The theft of cable television signals by unauthorized persons has plagued the cable television industry since its inception. New systems and methods are continually being developed to prevent signal theft. One category of systems for preventing signal theft utilizes a signal distribution apparatus for distributing CATV signals locally to various subscribers. Such a distribution apparatus is disclosed in U.S. Pat. No. 4,963,966 to Harney et al. Piracy is prevented by encasing the distribution apparatus in an enclosure and locating the enclosure off of the subscribers' premises. As a result, pirates have reduced opportunity to examine and effect changes to system circuitry of the signal distribution apparatus. The enclosures are capable of both aerial mounting on, for example, a telephone pole, or pedestal mounting for use at installations of underground cable or for placement in a locked room, for example. In addition, the enclosures contain tamper prevention circuitry for disabling the signal distribution apparatus when the enclosure is opened. When service of the signal distribution apparatus is necessary, the tamper prevention circuitry can be inhibited through a signal transmitted from the headend from which the broadband signal originates. A serviceman can then access the enclosure without disabling the signal distribution apparatus.
The signal distribution apparatus can perform such functions as premium channel interdiction in which an interfering signal is introduced into the television signal at a subscriber's location. This technique ensures that events carried on premium channels are available only to those subscribers authorized to receive the events. Such an interdiction system is described in U.S. Pat. No. 4,912,760 to West, Jr. et al. The signal distribution apparatus contains at least one microprocessor controlled oscillator and switch control electronics to secure several premium television channels. Control is accomplished by injecting an interfering or jamming signal into unauthorized channels from the pole-mounted unit. To improve efficiency and to save costs, one oscillator may be used to jam several premium television channels. This technique reduces the amount of required hardware and maximizes system flexibility. The oscillator output jamming signal frequency is periodically moved from channel to channel. Consequently, the oscillator is frequency agile and hops from jamming one premium channel frequency to the next. Costs are reduced since a single interdiction unit may serve a plurality of subscribers.
The cable television industry has additionally been pressured by subscribers to service defective system equipment promptly in order to minimize periods of signal loss. Accordingly, service of system equipment, including distribution apparatus, must be conducted around the clock. In order to reduce the costs of providing such comprehensive service, the number of employees and the amount of time needed to access and service a particular distribution apparatus must be reduced. However, if access is made easier, the distribution apparatus becomes susceptible to piracy. By the same token, systems and methods for preventing signal theft oftentimes make the service of distribution apparatus slow, inconvenient, and expensive. Accordingly, there is a desire in the industry to provide a signal distribution apparatus that prevents piracy but is still easily and efficiently serviced.